2. FIBER OPTIC BASICS
DID YOU REMEMBER TO DOWNLOAD THE
PDF FILE FOR FIBER OPTICS??? YOU
WELL NEED IT TO GET THROUGH THIS
COURSE
3. FIBER OPTICS – INTRO PART 2
Now that we have completed Part 1 of Fiber
Optics, in this part we well cover:
• Cable protects fibers in the application
environment
• Connectors join fibers or connect to active
devices so they can be disconnected for
rerouting, testing, etc.
• Splices join two fibers permanently
• Hardware provides the mounting, protection,
etc. for connectors or splices
• Test equipment checks performance
4. FIBER OPTIC CABLE
Because of the wide variety of conditions to
which they are exposed, optical fibers have
to be encased in several layers of protection.
The first of these layers is the primary buffer
coating, a thin protective coating made of
ultraviolet curable acrylate (a plastic), which
is applied to the glass fiber as it is being
manufactured. This thin coating provides
moisture and mechanical protection.
5. FIBER OPTIC CABLE
The next layer of protection is a buffer, that is typically
extruded over this coating to further increase the
strength of the single fibers. This buffer can be
either a loose tube or a tight tube. The next layer is
a strength member, usually an armored fiber, that
can be used for pulling the cable. Finally, the entire
cable is covered by a jacket designed to withstand
the environment into which the cable is going to be
installed.
Tight buffer (a zipcord is shown), distribution and
breakout cables are used indoors. Outdoors, loose
tube cable is used to allow filling the cable with
water-blocking materials to protect the fibers from
moisture.
6. FIBER OPTIC CABLE
CATAGORIES OF FIBER
• Tight buffer (Zipcord)
• Distribution
• Loose Tube
• Tight buffer Breakout
7. CABLE TYPE USAGE CHART
Type Application #Fibers
Tight buffer Building cable
Single fiber
Zipcord
Breakout
1-48
Distribution Building cable
Plenum
6-144
Loose Tube OSP
Aerial
Submarine
6-144+
Ribbon OSP
Aerial
Submarine
72-288+
8. TIGHT BUFFER CABLE:
Tight buffer cable is made in three versions:
• Single fiber, usually used for patchcords
• Zipcord used as a duplex patchcord for
connecting transceivers or connecting
devices together
• Breakout cable, which is simply a number of
single fiber cables inside a jacket used for
indoor cabling where each fiber is terminated
and routed directly to a connection.
9. TIGHT BUFFER CABLE:
• Distribution cable is an indoor cable that has
multiple fibers with a 900 micron buffer coating
which can be terminated directly, but lacking the
protection of the tight buffer cables above, must be
protected by enclosure in a patch panel or box.
• Loose tube cable comes in many varieties for
underground, aerial or even underwater
applications. It can also be armored for protection
against rodents for direct burial.
• Ribbon cable puts 12 or 24 fibers in ribbons and
stacks the ribbons to make a small diameter very
high fiber count cable. Applications are similar to
loose tube designs.
10. Fiber Optic Cable Selection
Criteria
• Cost
• Proper for the
application (building,
riser, plenum, aerial,
direct burial, submarine,
etc.)
• Enough fiber for
redundancy, upgrades
• Meets environmental
requirements
• Choose hardware to fit
cable needs
11. Fiber Optic Cable Selection
Criteria
Other factors to be considered when choosing
a fiber optic cable are:
1. Current and future bandwidth
requirements.
2. Acceptable attenuation rate.
3. Length of cable.
4. Cost of installation.
5. Mechanical requirements (ruggedness,
flexibility, flame retardanct, low smoke, cut-
through resistance).
12. Fiber Optic Cable Selection
Criteria
6. UL/NEC requirements.
7. Signal source (coupling efficiency, power
output, receiver sensitivity).
8. Connectors and terminations.
9. Cable dimension requirements.
10. Physical environment (temperature,
moisture, location).
11. Compatibility with any existing systems.
13. Specifications For Fiber Optic
Cable
Specifying the proper cable requires two major
considerations: (see next slide)
1. How the cable will be installed.
2. What environment it will be facing after
installation.
These are simply guidelines to consider when looking
for a cable for any particular installation. Different
manufacturers have different cable designs for
applications - and maybe different designs than
other manufacturers.
Therefore it is preferable to talk to several
manufacturers when choosing a cable, especially in
unusual situations.
14. Specifications For Fiber Optic
Cable
Installation
Specifications
– Tensile load
– Bend radius
– Diameter/
construction
– Temperature
Environmental Specifications
- Temperature
- Long term bend radius
- Electrical codes
- Long term tensile load
- Flame retardance
- Rodent penetration
- Water resistance
- Crush loads
- Abrasion resistance
- Resistance to chemicals
- Impact resistance
- Vibration
15. CHOOSING THE RIGHT FIBER
• Install the best
multimode fiber
• Include spare fibers
• Include singlemode
fibers in multimode
cable
• Include fibers in
copper cables (rare)
16. CHOOSING THE RIGHT FIBER
• The standard multimode fiber for over 15 years has
been 62.5/125 - the so-called FDDI grade fiber for it’s
bandwidth to support FDDI. There has been a revival
of interest in the earlier design 50/125 fiber for it's
higher bandwidth performance with VCSELs (up to
10 Gb/s), but it cannot be mixed with 62.5/125! If you
choose one fiber, all patchcords must be the same
fiber!
• Fiber is cheap - as cheap as kit string! When
specifying backbone cables, install lots of spare
fibers including singlemode fibers in multimode
cables for future high bandwidth applications.
• Sometimes it makes sense to put fibers into copper
cables. This is becoming more common when using
a combination cable (coax and UTP) for home
networks that may include 2 fibers.
